Author here. We study Moltbook's first-week snapshot (25k agents, 119k posts, 226k comments) and find that agent conversations follow a "fast response or silence" pattern — reply-kernel half-life is under one minute, 91% of comments never receive a direct reply, and threads are overwhelmingly star-shaped (mean max depth 1.38). A Reddit baseline analyzed with the same estimators shows substantially deeper threads and hour-scale persistence. We also test the widely discussed ~4-hour heartbeat hypothesis via spectral analysis but don't detect a significant aggregate periodic signal in this window. Code and data pipeline: https://github.com/AysajanE/moltbook-persistence